A PRIOR ART air brake system used on commercial trailers includes a trailer air brake actuated by an air chamber applying rotational force to an S-cam, which spreads the brake shoes open against a brake drum as the S-cam rotates, causing friction, and thereby retarding wheel rotation to cause braking. This known S-cam is part of an axle assembly and is typically supported on each end through small S-cam bushings, which keep the S-cam centered relative to the brake shoes, while allowing the cam to rotate freely.
Once those components are worn, the performance of the overall brake system is diminished, resulting in accelerated brake and drum wear and loss of braking power. Replacement of S-cams and S-cam bushings is costly and involves major dismantling of the wheel assembly.
PRIOR ART S-cam systems are subject to wear owing to vibration and high twisting loads exerted on the S-CAMs and S-CAM bushings.
PRIOR ART S-cam and S-cam bushings, which support the S-cam shaft near its ends, distribute these loads over a small surface area relative to the S-cam shaft surface area, and once these bushings wear, the S-cam bushings, and often the S-cam must be replaced.
PRIOR ART shafts which are machined smooth only on the ends, such as in the form of machined journals, can only be provided with bushings on the smooth machined outer ends. Given the rough finish of the PRIOR ART shafts in the middle, no bushing can be provided in the middle.